G. Tiravanti

Lead removal and recovery from battery wastewaters by natural zeolite clinoptilolite

ABSTRACT Technical feasibility of an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated. In absence of aluminium and ferric species, lead is quantitatively removed and recovered (≈90%) from the neutralised wastewaters after elution on the natural zeolite clinoptilolite. Control of pH to 5.5-6 is necessary to minimise degradation of the exchanger material. Throughput volumes exceeding 2,700 bed volumes (BV) (flowrate: Fexh10 BV/h) is obtained, when the initial Pb concentration is 4 mg/L, with the metal leakage steadily below the maximum allowable concentration (MAC<0.2 mgPb/L) set by the EU for discharge in rivers, lakes, coastal seawater. Regeneration of the zeolite is carried out by controlled elution of limited amounts of IM NaCl, pH 4.5 (40BV, Freg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recovered to the battery manufacturing operations. This latt...

Degradation of herbicides (ametryn and isoproturon) during water disinfection by means of two oxidants (hypochlorite and chlorine dioxide)

The paper reports the results of an investigation aimed to find out the number and the chemical structures of byproducts which form during the reactions occurring in aqueous solution between two very common disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO 2 ), and two herbicides widely used in agriculture and frequently found in groundwaters: ametryn and isoproturon. Under controlled experimental conditions [T=20°C, pH=7, reaction-time = 48h, herbicide/disinfectant molar ratios: 0.05 and 0.05×10 −2 ], ametryn reactions with chlorine dioxide much slower than with sodium hypochlorite, whereas the opposite trend has been observed for isoproturon. In any case, however, the higher the reagents concentration the faster the reactions. As for reaction byproducts, they have been detected by HPLC and identified by HPLC-MS. In particular, ametryn (R-S-CH 3 ) reaction with NaClO gives rise to the consecutive formation of four derivatives: the sulphoxide (R-SO-CH 3 ), the sulphone (R-SO 2 -CH 3 ), the sulphonate ester (R-O-SO 2 -CH 3 ) and its hydrolysis product (R-OH). Within the fixed reaction time (48h), ametryn reaction with ClO 2 forms only the sulphoxide derivative (R-SO-CH 3 ). As for isoproturon, it reacts with both oxidants forming aromatic-ring substituted derivatives. In particular, during the reactions with NaClO and ClO 2 , four and two (chlorinated and/or hydroxylated) derivatives are respectively formed.

Pb/Fe SEPARATION AND RECOVERY FROM AUTOMOBILE BATTERY WASTEWATERS BY SELECTIVE ION EXCHANGE

ABSTRACT Laboratory scale investigation has been carried out for the optimization of a new process for separation and recovery of Pb/Fe species from automobile battery manufacturing wastewaters. The innovation, based on ion exchange, allows for separation and recovery of the mentioned species by the use of a commercial weak anion resin (Duolite A7 from Rohm&Haas Co, USA), as selective sorbent for the ferric species, and a weak cation resin with carboxylate functionality (Purolite C106 from Purolite Co.,UK) for removal and recovery of lead species. Cl-form anion resin was eluted with real automobile battery wastewaters (pH 3; Fes= 4BV/h; influent Fe concentration: 2 mg/L) for a column throughput exceeding 200 BV (Bed Volumes) with Fe leakage steadily below 0.2 mg/L, (ten times lower the maximum allowable concentration, MAC, for discharge in closed water bodies, enforced by EU legislation). Lead species were removed and recovered on Na/H-form cation resin (pH 6; Fexh=20 BV/h; influent Pb concentration: 4 mg/L) for a column throughput exceeding 15,000 BV at average Pb leakage below 0.03 mg/L (MAC=0.2 mgPb/L). Both sorbents were regenerated by limited amounts of 1M HC1. Specifically, resin Duolite A7 was eluted with 5 BV (Freg =2BV/h), and carboxylate resin was eluted with 30BV

Cr(III)/A1(III)/Fe(III) ion binding on mixed bed ion exchangers. Synergistic effects of the resins behaviour

Abstract Ion exchange, as a conservative technology, allows for removal and recycling of metals from liquid effluents. Chelating exchangers may be used to the purpose due to their specificity toward metal species. The specificity, related to the metal-functional group affinity and thus the high stability of the complexes formed, is paid in terms of regeneration levels necessary to reverse the exchange reaction by mass action. Moreover, the liquid-phase speciation of the metals with organic and inorganic ligands, commonly present in industrial effluents, determines the active metal concentrations at the binding sites and thus the removal efficiency of the chelating resins which is, in general, more affected by stereochemical factors during the interaction of the active species at the functional groups. In this context, we investigated the behaviour of a mixed bed weak electrolyte anion (amino) and cation (carboxylate) conventional ion-exchangers as an alternative to chelating resins. The synergistic effects of the two functional groups to selectively remove, separate and recover Cr(III), Al(III), Fe(III) from segregated industrial effluents are discussed. The exhaustion behaviour of the carboxylate resin toward chromic and aluminum species is synergized by the cooperative presence of the anion resin, this latter being able to selectively retain ferric species. Difficult regeneration behaviour of the metal-form carboxylate resin is also favored by the presence of the weak base amino functional groups in the free base form.

STDS study for the identification of released compounds from commercial ion-exchange resins

Abstract Physical and chemical stability of polymeric sorbents, including ion-exchange resins, is among the main concern of both manufacturers and users. Different countries are gradually introducing regulations for the use of ion exchangers in water conditioning, food and beverage processing, separation of pharmaceutical products, and also for the use of reference materials as drugs and medical devices. Since all the applications mentioned may directly influence human health, the treated products must be free of any trace toxic compound potentially released by the polymeric matrix of the sorbent. The System for Thermal Diagnostic Studies (STDS) has recently been introduced commercially as a new versatile and powerful technique for the identification of the products evolved after thermal stress of solid phases. In this paper are presented the results of an STDS investigation to simulate the release of organic compounds from commercial weak and strong electrolyte anion and cation resins, differing for the type of polymeric matrix (polystyrene and polyacrylic based), porosity (gel and macroporous type), and functional groups, including sulfonic and carboxylate functionalities for the cation resins, and secondary, tertiary amine and quaternary ammonium functionalities for the anion resins. STDS determinations were carried out at 130, 200, 250 and 300°C by using a constant reaction time (10 min) and an inert (He) gas atmosphere. The thermally released compounds were cryofocused at −60°C and separated by temperature-programmed gas chromatography. The qualitative identification of the released compounds was made by searching the MS library NBS 54K. Thermogravimetric determinations were also carried out on a set of cation resins to complement STDS data.